Resonant screen



May 2, 1967 1 a. A. CENTURY 3,

RESQNANT SCREEN Original Filed Nov. 24, 1961 4 Sheets-Sheet 1 FIG.

F I G. 2-

m Q \Q Q "Q q. Q INVENTOR.

BERNARD A- CENTURY May 2, 1967 B. A. CENTURY RESONANT SCREEN 4 Sheets-Sheet 2 Original Filed Nov. 24, 1961 IN VEN TOR. BERNARD A. CENTURY it n May 2, 1967 A. CENTURY RESONANT SCREEN 4 Sheets-Sheet v Original Filed Nov. 24. 1961 mm WM INV EN TOR. BERNARD A, CENTURY y 1967 B. A. CENTURY 3,317,041

RESONANT SCREEN Original Filed Nov. 24, 1961 4 Sheets-Sheet 4 F I c. 9;

.SPEED INVENTOR.

BERNARD A. CENTURY United States Patent Continuation of application Ser. No. 154,691, Nov. 24,

1961. This application Oct. 5, 1965, Ser. No. 502,806 13 Claims. (Cl. 209-315) This application is a continuation of application Ser. No. 154,691, now abandoned, filed Nov. 24, 1961, titled, Improvements in Vibratory Screen Systems.

This invention relates to a two mass system vibratory screen, and in particular, to such a screen having a soft suspension spring system supporting each mass independently, and which includes a non-linear inter-mass spring system of free resonant type.

Resonant screens, for conveying and classifying operations, are becoming increasingly popular. The use of resonant principles enables construction of larger, greater amplitude machines than obtainable with other known methods, and machines which operate with higher amplitude, but with relatively small size motors and drive mechanisms. There are many types of these resonant devices. Perhaps the primary characteristic separating these types relates to the number of masses, as virtually all are either of the single or double mass variety.

With the single mass resonant machine, all of the dynamic forces are transmitted to the supporting structure. This restricts the single mass variety to light machines operating at low values of acceleration and which must be mounted on very sturdy structures. The two mass system is not so restricted.

Two mass resonant screens may be classified according to the degree of linearity of the inter-mass, main spring system. A means of distinguishing them may be better understood by referenceto FIGURES 9 and 10 of the drawings which show Deflection/ Load and Speed/Amplitude curves, respectively, characteristic of three inter-' mass spring systems. In both figures, curves a are typical of the action of a linear spring, such as undamped steel coils or rubber in shear. Steep resonant characteristics are indicated by curve a'in FIGURE 10. Curves b and curves 0, in FIGURES 9 10, are representative of nonlinear springs. These curves show that variations of load, or running speed, will have a greater effect on the operation, and particularly the stroke (amplitude), of a linear system illustrated by curves a, than on a non-linear system illustrated by curves b and c. The linear system is inferior to the ncn-linear system for handling materials of any reasonable quantity, because of the steepness of the resonant curve of a linear system. Variations of material load or running speed 'will result in large stroke variations.

A superior non-linear system is one having the characteristics illustrated by curves 0. This is accomplished in one instance by using spaced apart rubber buffers in the inter-mass system which allow the masses to negotiate part of their vibratory cycle without application of accelerating forces. This system can thus be termed free resonant, because during part of the operation, the resilient members are free of, that is, do not contact, each other. The system illustrated by curves c in FIGURES 9 and 10, in contrast to that illustrated by the curves b of FIGURES 9 and 10, is characterized by a broader and flatter operating curve, capable of accomplishing sharper material sizing. Among the advantages achieved through perfecting a curve 0 type system are the much lower cost of the spring system and its supporting members, and the ease with which maintenance and shrouding may be accomplished.

In the preferred construction of a battery for a free resonant system (a battery being defined as the main intermass springs and their supporting members at a single "ice station), four spaced apart bufi'ers or snubbers are used. Two buffers are shaft mounted and attached to one mass, and two are fastened to the other mass. There are other equally effective arrangements: two buffers per battery, both. fastened to the top mass; two buffers per battery, both fastened to bottom mass; two buffers per battery, one fastened to top mass, and one to the bottom mass, etc.

Another manner of distinguishing two mass resonant machines takes into consideration the type of guidance system used. The most efficient system involves the use of leaves or rocker arms, which interconnect the masses. These means are oriented at right angles to mass motion and main spring action, and link each mass through their end connections. Considerably less desirable is a guidance system in which there is a link to ground from one or more of the masses. This can come about by having separate mass guidance wherein one end of the means employed is connected to ground, or whereby the nodal point of an inter-mass guidance means is fastened to ground. In either of these cases, where there is a link to ground, a separate, or third, frame is required, and manufacturing precision must be of a higher order. The device of the subject invention utilizes a leaf type intermass guidance system and the sole purpose of the components of the system is guidance. They do not act at all in supporting the dead weight of the frames.

Yet a further tool for distinguishing features of the two mass resonant systems is found in the ratio of weight of the two masses of the system, recognizing that the amplitude of vibration of a given mass is inversely proportional to its weight. In other words, if both masses are equal in weight, they will have equal strokes and both will be capable of working on the material. If, however, the secondary mass is three times as heavy as the primary, and the primary has a reasonable stroke forconveying or screening, the secondary mass, by virtue of the fact that its stroke will be one-third that of the active deck (because amplitude is inversely proportioned to mass) will be useless.

In general, a further compartive advantage of equal weight to mass systems is that the 1:1 system will weigh one-half of the 1:3 system. Most of the heretofore known two mass systems are of the 1:3 variety. One supposed advantage heretofore ascribed to such systems, since the system is usually spring mounted from its heavier mass, is that less vibration is transmitted to the foundations than if the masses were 1:1. While it is true that the amount of dynamic amplitude to which the mounting spring is subjected is less than in the 1:1 system, this feature is almost balanced by the fact that the overall mounting spring systems must be twice as stiff for the :3 system. Another factor which should not be overlooked is that the system of the subject invention, which has a 1:1 mass ratio, can and does have, as a consequence, two useful masses, and weighs half that of the 1:3 system. If a 1:1 screen were spring supported from one mass only, it would subject the foundations to 50% more vibration than the 1:3 system, however, according to my invention each mass is individually supported on its foundation.

Another characteristic of two mass resonant machines which can be used to distinguish them resides in the disposition of the two masses. First, it should be recognized that according to known techniques a 1:1 system may have one mass disposed within the other. Only one mass can be used for screening or conveying in such an arrangement.

One method of obtaining a fully utilizable 1:1 system is to have both masses of roughly equal width and length, and to have one disposed directly above the other, as in the form of the preferred embodiment of this invention.

3 A 1:1 system that allows one mass to surround, or go through, or be outside of, the other mass cannot be fully utilized.

As mentioned previously, the prevalent type of resonant screen is a two mass system of mass ratio 1:3. The light, active mass, is usually placed above the heavy base mass, and support of the unit from ground is achieved by use of resilient springs beneath the base mass. The amount of vibration force that the supporting structure will receive is a function of the total supporting spring stiffness and the amplitude of base frame vibration. In any event, where the benefits of stroke stability are required, a nonlinear, inter-mass main spring system characterized by the b or c curves of FIGURES 9-10 must be used. The most modern machines will utilize systems of the c curves.

It will be recognized by those skilled in the art that in a system in which the static load of the upper frame is to be carried by the battery springs and the guidance springs, the static load is detrimental to the life of the battery springs. One artifice sometimes used to eliminate this effect is the use of an auxiliary upper deck holdup spring. This spring, oriented between masses and along the main spring line of action, supports the upper deck component of weight along this line of action and thus relieves the battery springs of the detrimental static component of force. A very novel feature of the subject invention accomplishes the above function, namely relieving the main battery springs of static loading. According to the invention each mass is totally and independently supported from ground. In this way, it can be seen that both main spring and guidance systems are relieved of all static forces, and the supporting springs are only subject to a strain corresponding to a single mass motion, rather than to a strain corresponing to the total motion.

The mounting springs employed are resilient in all directions and they are the only connection of the frames to ground. It will thus be recognized that precision in locating the mounting means is not required, nor is the use of a third or base frame. Not the least important of the advantages of this means of mounting employed is the extra degree of vibration isolation that is produced. It will be appreciated that a two mass system is one in which the masses operate out of phase with one another. According to the invention, masses of substantially equalweight are used and similar top and bottom mounting springs are also employed. The net foundation forces are accordingly nil.

Resonant screens and conveyor systems of any type include an exciter. Such a device supplies power to the system, in other words, replenishes the losses of operation. Among the common type of exciters used are two bearing unbalanced pulley types, and four bearing crankshaft types with a resilient connecting rod. Either type of exciter will operate any kind of known resonant screen, albeit that there are advantages and disadvantages to both. Any one of the known eXciters can be used with a screen of the kind disclosed herein.

Among the advantages of a vibratory screening device, according to this invention, are that it will weigh half the amount and will present twice as much screening area to the material as those of the types heretofore known, the main spring and guidance systems are relieved from all components of static strain because of its novel mounting arrangement, and foundation isolation is achieved.

It is an object of this invention to provide a vibratory resonant system of equal masses with each mass being an active screen deck, i.e., with each of the said active screen decks constituting an effective screen area.

It is another object of this invention to provide a vibratory system having active screen decks with a novel interdeck system.

It is a further object of this invention to provide an interdeck system which has a long, useful life, and which is so constructed and arranged with respect to the active masses as to effectively transmit vibratory forces.

It is a still further object of this invention to provide a vibratory screen system with active decks, each of which is independently and resiliently supported, whereby substantially zero ground vibratory forces are transmitted by the system, and which is, at the same time, compact.

Other objects and advantages will become obvious to those skilled in the art from a reading of the specification taken in connection with the accompanying drawings, in which:

FIGURE 1 is a side elevation view, with certain portions exposed, illustrating the overall relationship of the active screen decks and the novel suspension system of this invention;

FIGURE 2 is an end elevational view of the assembly shown in FIGURE 1;

FIGURE 3 is a partial plan view illustrating the upper screen deck, with a portion of the screen cloth cut away to expose the sub-structure of the screen deck;

FIGURE 4 is a partial, enlarged side elevation illustrating in detail the battery, guidance, and support spring assemblies of the novel suspension system of this invention associated with two active screen decks;

FIGURE 5 is an enlarged cross-sectional view of the novel battery assembly taken along line 55 of FIG- URE 4;

FIGURE 6 is a cross-sectional view along line 6-6 of FIGURE 5 illustrating the relationship of the upper screen deck cross-bar and the battery assemblies with respect to a side wall of the upper screen decks;

FIGURE 7 is an enlarged cross-sectional view along line 7-7 of FIGURE 4, further illustrating some of the elements of the battery assembly;

FIGURE 8 is a fragmentary enlarged view illustrating another embodiment of the guidance spring system;

FIGURE 9 is a graph of Load plotted against Deflection, comparing linear and non-linear inter-mass spring systems; and

FIGURE 10 is a graph of Amplitude plotted against Speed comparing linear and non-linear inter-mass spring systems.

In its broadest aspects, this invention comprises two active screen decks of substantially equal masses, in dividually and resiliently supported, having an interdeck non-linear resonant spring system, whereby both active screen decks may be resonantly agitated at substantially equal amplitudes for performing a classification and/or conveying operation.

The general arrangement of the vibratory screening apparatus of this invention comprises individually supported upper and lower active screen decks provided with suitable exciter means supplying vibratory energy for agitating the screen decks. In addition, a novel resonant spring system becomes operative when the active screen decks vibrate within their natural resonant frequency range. The entire assembly may be mounted on a suitable steel frame or base, or may, if desired, rest upon the ground or floor in the area in which it is to be used.

Referring to FIGURE 1, the vibratory screen system of this invention is shown generally at 10. Two generally rectangular screen decks are shown, with the upper screen mass designated 12, and the lower mass, as 14. These screen decks are of substantially the same size and mass. The upper screen deck is composed of longitudinal side panels 16, and the lower screen deck has similar longitudinal side panels 18. Suitable end walls may also be provided, if desired. The upper and lower decks are also provided with suitable discharge lips 24 and 26.

Each of the screen decks 12 and 14 is also provided with a screening cloth 28 and 28, respectively, supported within each deck frame. These cloths are removably secured within each of the frames, as is well-known, and rest upon longitudinal supports 30 (see FIGURE 3). Transverse connecting members 32 are secured to the side panels of each of the deck frames and serve to support longitudinal struts 30 as well as interconnect the side 'for any particular classification operation.

The apparatus for supplying motive power to the screen decks may be provided at one end of the screen decks. Referring to FIGURES 1 and 4, it will be seen that the motive power means includes an electric motor 40 having a multi-sheave pulley 44, secured to one end of the motor drive shaft. Mounted in brackets located at one end of the lower deck frame is a shaft 48 whose longitudinal axis is transverse to the lower deck frame, which is also provided with a pair of multi-sheave pulleys, 46, at each end thereof. Rotational energy is applied to shaft 48 through one of the pulleys 46 by means of a belt 50 which passes around pulleys 44, 46, as shown in FIGURE 1. Secured to shaft 48, and rotatable therewith, is an eccentric element 52 whose axis is parallel to, but displaced from, the axis of shaft 48. One end of exciter arm 54 is suitably connected to eccentric 52 with the other end of the exciter arm connected to the elastic element 56 located, in the embodiment shown, on the upper active screen deck. Exciter arm 54 is connected to eccentric 52 and elastic element 56 such that rotational motion of the eccentric element 52 is transmitted to elastic element 56 in the form of rectilinear motion, as is well understood. In this way, vibratory motion is transmitted to the screen decks.

Elastic element 56 may be any of the conventional elastic excitation elements commonly used in resonant screen systems. For example, element 56 may be comprised of a plurality of rubber sandwich elements, or of a plurality of rubber cylinders. In any case, the exciter will be capable of sustaining full vibration with only a small power requirement once resonant conditions have been achieved, and the system may be started with a normal size motor.

The motive power means and the exciter assembly, per se, form no part of this invention, as many of the conventional resonant screen vibratory motive systems may be utilized within the spirit of the invention.

The novel screen system of this invention comprises essentially four sub-assembly units; the guidance spring system, the reaction spring system, the support spring means, and two equal screen masses, described above.

Referring to FIGURE 1, the guidance springs, according to the embodiment of this invention, will now be described. Secured to a side panel 16 of the upper deck 12 is an upper spring bracket 62 which is inclined from the horizontal in the manner shown. Located on side panel 18 of the lower deck frame 14 is a similar bracket 64 axially aligned with upper spring bracket 62. Positioned between upper and lower spring brackets 62 and 64, and secured thereto, are leaf spring elements 66. The upper end of these elements is secured to upper spring bracket 62 by means of upper leaf spring clamp plates 63, and the lower end of these elements is secured to the lower leaf spring bracket 64 by means of a lower leaf spring clamp plate 65, similar to clamp 63.

i In practice, it has been found desirable to mount guidance springs on each of the longitudinal sides of the screen conveyor apparatus. As illustrated in FIGURE 1, the guidance springs are mounted on the side panels substantially near each end of the deck frames. On the other, or far, side of the frames, another set of two guidance springs will be found. Preferably, the guidance springs should be mounted in pairs, one pair on each side of the frame with the springs of each pair in opposed relation, (see FIGURE 3). It should be understood that the number of pairs of guidance springs may vary dependent primarily on the size and capacity of the screen deck frames. The guidance springs are capable of flexing, and may be suitably made of plywood strips, as is well known in the art. The guidance springs act as positioning means for maintaining the two decks in their proper relative positions during vibration.

According to another embodiment, see FIGURE 8, leaf spring elements 106 are secured at their upper end to an upper spring bracket 108 located substantially near the upper edge of the upper screen deck. Leaf spring elements 106 are secured at their lower end to lower spring bracket 110 located near the upper edge of the lower screen deck. In this embodiment, the leaf spring elements span the width of the upper screen deck side panel and the distance between the upper and lower screen decks, but extend only to the upper edge of the deck frame. The guidance means of the embodiment of FIGURE 8 is similar with respect to its function and symmetrical arrangement concerning the location of the leaf spring elements along the length of the side panel, and on each side of the deck frames, as described for the guidance means illustrated in FIGURE 1. In both embodiments, the leaf spring elements are connected so that they are capable of a small degree of flexing.

The reaction spring system of this invention will now be described. The relationship of the reaction spring system with the guidance and supporting spring systems is generally illustrated in FIGURES 1 and 4.

The principal components of any reaction spring system utilized in resonant screening devices comprise the battery structure and the buffers or snubbers themselves. The battery assemblies should be arranged in opposed pairs, with one battery assembly on each longitudinal side of the deck frames, as with the guidance spring means. Each of the batteries may be encased in suitable safety housings 79 to exclude dust and other debris resulting from screening operations. Although the description of the battery assemblies will, in general, be con fined to only one assembly, it should be understood that the description is applicable to each of the battery assemblies.

Referring to FIGURE 4, it will be noted that affixed to side panel 16 of upper deck 12 are battery angles 68, 69. Angles 68, 69 are inclined from the horizontal and are spaced apart, as shown. Secured to side panel 18 of lower deck frame '14 are lower deck battery angles 70, 71 which are also spaced from each other. The distance between angles 70, 71 is greater than the distance between battery angles 68, 69. Battery angles 68, 69 and 70, 71 are axially aligned with their axes at right angles to the axes of the leaf spring elements 66 forming a part of the guidance spring means. The upper end 72 of battery shaft 73 is rigidly secured to and located between upper battery angles 68, 69. The upper end 72 of shaft 73 may conveniently be rectangular to obtain a more rigid connection of the shaft to the battery angles. The lower end of shaft 73 is threaded as at '74, and is adapted to receive the spring elements or snubbers of the battery assembly.

In the preferred form, two pairs of snubbers 89, and 91, 92 are used in each battery (see FIGURES 4 and 5). These snubbers are resilient members, made, for example, of rubber, and in the preferred embodiment, are in the form of truncated cones having an enlarged tapered bore therethr-ough. Within each pair of snubbers, as 89, 90, the smallest bases face, and are spaced apart from, each other.

An upper shaft nut 76 -is threaded onto the upper end of threaded portion 74 of shaft 73. Also threaded on the threaded shaft portion 74 below nut 76 is an upper adjustment collar 78 to which is secured upper striker plate 80. Firmly affixed to plate 80' is snubber 89. At the lower threaded end, 74, of shaft 73, is lower shaft nut 83, and lower adjustment collar 86 to which is secured lower striker plate 84. Firmly affixed to plate 84 is snubber element 92. Interposed between snubber elements 89, 92 and locate-d along the threaded end 74 of shaft 73 is snubber bracket 82. The threaded portion 74 of shaft 73 freely passes through an enlarged hole 87 (see FIGURE 7) formed in the snubber bracket 82. The snubber bracket 82 is secured to the lower deck battery angles 70, 71. On the upper side of snubber bracket 82 is secured snubber element 90, and to the lower side is secured snubber element 91. Preferably, the space between the snubber elements of one pair should be equal to the space between snubber elements of the other pair. The space between each pair of snubber elements may be varied by proper adjustment of upper and lower shaft nuts 76, 88 and adjustment collars 78, 86.

As is well known, at one point in the oscillatory cycle of movement of the upper and lower deck masses, they will be at a maximum distance apart from each other. When shaft 48 rotates 180 from that point, the upper and lower deck masses will be at a minimum distance apart. The battery assemblies are constructed such that there will be substantial clearance between the inactive pairs of snubbers at these two intervals. Thus, when the two decks are at a maximum distance apart, the two upper snubbers, 89 and 90, will be at the maximum distance apart and the two lower snubbers will be in contact, whereas when the two decks are at their closest approach to each other the two lower snubbers, 91, 92, will be at the maximum distance apart and the two upper snubbers will be in contact.

The enlarger hole 87 of bracket 82 through which the shaft 73 passes permits free movement of air into or out of the central chambers 95 within the snubber elements. This structure leads to an important advantage in that it greatly reduces heating, and eliminates the possibility of high stress points within the elastic snubber elements. The heretofore known constructions utilizing solid elastic buffer members did not possess these advantages. For example, in one well-known form of screen system, apertures are provided extending laterally through the elastic buffer elements from internal chambers to the exterior circumferential surfaces to permit the flow of air through the elements. This, however, as will be understood, resulted in stress concentrations in the elastic elements, causing them to fail along the aperture locations by progressive deterioration and cracking. The battery system of this invent-ion thus has a marked advantage in that it is cooler running and longer lasting than heretofore known batteries.

One other important advantage of the instant invention resides in the means for transmitting the battery forces to the screen decks. In particular, this is to be noted with respect to the transmission of forces from shaft 73 to the screen deck 16 adjacent the upper end of the shaft 73. Referring particularly to FIGURES 4, and 6, it should be noted that the upper screen deck side wall is slotted and receives a fork 114. The two legs of this fork are connected by nut and bolt means 116 to the upper battery angles. Suitable spacing means are provided to position fork 114 centrally within the angles 68, 69. At its opposite end, the fork 114- has a series of openings adapted to receive suitable bolts for connecting the fork to the channel cross-bar 112. The side plates of the deck frames are interconnected by cross beams, 32, which aid in supporting the screen cloth. In many instances, the screen cloth is supported by bucket-up bar holders 34 which support longitudinal rods 30. Rods 30, in turn, directly support the screen cloth. By this structure, it is possible to achieve curvilinear upper screen surfaces without the use of expensive curvilinear structural members. Further, the longitudinal rods 30 provide support for the screen cloth longitudinal along the deck between the structural cross beams 32.

According to this invention, the cross beam 112 and its forked connecting plates provide a means of resisting the tendency of the deck plates to twist, because of the eccentricity of the applied load. It should be noted that the force of the bar 73 is applied by the upper battery angles directly to the side plates 16 of the upper deck 12. However, the cross-bar 112 stabilizes the upper deck and prevents twisting of the side plates. At the same time, cross-bar 11.2 functions as one of the normal cross beams interconnecting the side plates to the deck frames. In heretofore known constructions, an additional member has been employed for the purpose of transmitting battery forces or controlling the eccentric loads. In one instance, for example, a oross-bar is placed above the deck and in another instance, below the deck, While in still other types of screen systems, an additional member is inserted through the deck and partially extends either above or below the deck frame. With this invention, however, an additional cross beam is not required, and the vertical clearance between the decks is not adversely affected or reduced. With separate elements positioned between the decks, as in some known systems, the suspension system becomes more complex, because the decks must be spaced further apart for the same degree of movement. As the space occupied by a screen is often of a limited nature, it may be readily understood that unnecessarily increased screen height is not desirable. In addition, where elements extend across the top of a screen deck, for example, the upper deck, access to the upper deck is reduced which creates problems in loading the upper deck, and in removing or adjusting the screen cloths.

Other advantageous aspects of this invention will now become apparent; i.e., the symmetrical arrangement of the system, and its compactness, coupled with maximum utilization of the elements forming the system. It may be readily noted that the battery angles are also connected to the lower deck cross beams 32 facilitating stability of the overall system, as well as increasing the strength and the life of the lower deck. The construction which permits easy access to the upper deck, also provides for easy access to the lower deck, and permits ready removal of the screen cloth from the lower deck.

Referring to FIGURE 4, the supporting spring means will now be described. The structure secured to the lower battery angle 71, is a bracket 94. Interposed between pedestal 102 and bracket 94 is spring 98. Also secured to pedestal 102 is a vertical upstanding support 100, having a platform 101 aflixed to its upper end. Secured to panel 16 of upper deck 12 is a bracket 93. Inter-posed between platform 101 and bracket 93 is another support spring 96.

The support spring structure, including springs 96 and 98, is located near each end of the deck frames, and on both sides of the deck frames. Preferably, the supporting spring structure is utilized in pairs with one pair of springs 96, 98 on each side, and with each set of each pair in opposed relation, as was described above for the guidance spring means and the reaction spring system.

Springs 96 support upper deck 12, and springs 98 support lower deck 14. These springs provide a resilient suport for each of the decks, and serve to maintain the spaces between the pairs of snubbers in the battery assemblies, when the decks are at rest. In this way, the invention provides a resilient support structure for the decks which insures that no detrimental load is placed on the resilient snubber elements when the decks are at rest. The supporting springs 96 and 98 maybe made of rubber, or may be comprised of steel springs.

It will be clear that the simple suspension system described above allows for other very important advantages: (1) the relief of the guidance springs and battery springs from the static components of strain, and (2) virtual elimination of foundation force transmission. Although some known free resonant screens achieve the first advantage by inter-posing a suspension spring between the two masses so as to support one from the other, such a technique does not achieve the second advantage, and further imposes a needless high strain on the interdeck spring. It should also be recognized that these two advantages are gained without the need for accurate placement of the machine or its components upon a supporting structure, permits ready installation of the unit directly on the plant floor or ground.

Although the invention has been described with particular reference to specific embodiments, the same are not to be construed as in any way limiting the invention. Reference is, therefore, to be had solely to the appended claims for the purpose of determining the scope of the invention.

I claim:

1. A free resonant vibratory screening device comprising a pair of frame members, each of said members being substantially of the same mass as the other said members, each of said frame members containing a screen mounted therein being capable of performing a screening function when agitated or oscillated, said members being positioned one above the other and resilient means supporting each of the said members independently of the other, the resilient means supporting one member having a spring rate, the resilient means supporting the other member, having a spring rate, the spring rate of one resilient means being so related to the spring rate of the other resilient means that the net operating vibratory forces transmitted to the ground by the resilient means supporting one member are substantially equal to the net operating vibratory forces transmitted to ground by the resilient means supporting the other member, an interdeck battery system, means for exciting said frame members at a frequency which is substantially the resonant frequency of said frame members so as to cause movement of each of said frame members in opposite directions with respect to the other, said interdeck battery system comprising a first pair and a second pair of buffer members; the buffer members of said first pair being connected respectively to one of said frame members, the buffer members of said second pair being connected to the other of said members, the buffer members of one pair each being in facing relationship with one of the buffer members of the other pair; to thus form opposed pairs of facing buffer members, the facing buffer members being movable toward and away from each other during the relative movement of said frame members with respect to each other, the movement being of such nature and amount such that buffer members of one of said opposed facing pairs contact each other and are deformed sufficiently to absorb the total energy of both said frame members during movement of said frame members in one of said opposite directions and to bring said frame members to a stop, and said elements being of a nature such that they will then immediately thereafter start to return to said frame members substantially all said energy and thereby cause said frame members to move in opposite directions with respect to the prior direction of opposite movement relative to each other, and the spacing between said facing buffer members being such that they will, while said masses are moving in the latter direction, respectively, move away from each other out of contact wit-h each other and said buffer members will be restored to their original shape, the other of said opposed pairs of buffer members being arranged with respect to each other and said frame members and be spaced in such a manner that they will thereafter come into contact with each other and be deformed and absorb the entire energy of movement of said frame members in said opposite directions with re-' spect to the prior direction of opposite movement and bring said frame members to a stop and said other of said opposed pairs being designed so as to then restore immediately substantially all the energy previously applied to the frame members and cause the latter to move in the first mentioned opposite direction with respect to each other, guidance means connected to said frame members adapted to maintain movement of said frame members in a preferred path, said buffer members being related so as to form a non-linear inter-mass spring system with the spacing between the buffer members of both said facing pairs being such that one pair of said facing pairs of buffer members does not come into contact until a period of time spaced from the period of time in which the contact between the other said facing pairs of buffer members has been broken.

2. Apparatus according to claim 1 in which said buffer members connected to one of said frame members are positioned between the two buffer members connected to the other of said frame members, a connecting member attached to and extending from said one of said frame members through the two buffer members connected to said other of said frame members and interconnecting the two buffer members connected to said one of said frame members to the latter.

3. The apparatus of claim 2 wherein said connecting member is spaced laterally along its length from the buffer members connected to said other of said frame members and there is room for the passage of ambient air along said connecting member between it and the latter said buffer members.

4. The screening device of claim 2 wherein said connecting member extends through the buffer members connected to said one of said frame members and is spaced laterally from the latter said member by a distance adequate to provide for entrance and exit of ambient air between said connecting member and the latter said buffer members.

5. The apparatus of claim 2 wherein the buffer members interconnected by said member are each adjustable along the length of said connecting member for adjustment of the spacing of the latter bufier members relative the buffer members connected to said other of said frame members.

6. The apparatus of claim 1 wherein said resilient supporting means support said frame members in a manner so that all of said buffer members are out of contact with their facing members when said device is at rest.

7. A resonant screen device, comprising, in combination: a pair of vertically spaced screen decks movable relative to each other, each of said decks having side plates and cross beam members and screens supported by said cross beam members, the cross beam members of each deck being connected to the side plates of its associated deck; an interdeck battery system comprising buffer members including resilient elements; means connecting said resilient buffer elements to said decks for reaction between said buffer elements within the resonant range of operation of said decks; said connecting means including one of said cross beam members of one of said decks and an operating rod connected to the latter cross beam member, said rod extending alongside of said screen decks; at least one of said buffer elements being connected to said rod and at least one of said buffer elements being connected to the other of said decks, the latter of said element-s being reactable with said one of said buffer elements to cause interdeck action when said screen is oscillated in the resonant range.

8. The screen device of claim 7, wherein said rod is also connected to said one of said decks by means secured to a side plate of the latter deck.

9. A resonant screen device of the character described in claim 8, wherein the means interconnecting said operating rod and its associated said cross beam comprises a fork member extending through the latter side plate adjacent the beam-rod connection so as to provide effective connection of said rod to the latter said cross beam along a length of said rod.

10. A resonant scren device of the character described in claim 7, wherein the means connecting said at least one of said buffer elements to the other of said decks comprises a bracket member extending laterally of said rod, said rod extending through said bracket member; means connecting said bracket member to the said other of said decks comprising mounting angles; and means connecting at least one of said angles to one of the cross beams of said other of said decks. I

11. A resonant screen device of the character described in claim 10, including suspension means for said decks for individually supporting said decks from a base relative to which said decks are adapted to move; said suspension means comprising a support; resilient members extending upwardly from said support, one of said resilient members serving to support said other of said decks by means connected to the latter resilient member and one of said angles of the latter deck; means supportingly connecting another of said resilient members to said one of said decks comprising a connecting member for transmitting the reaction load from the latter resilient member and its associated angle and cross beam to said rod.

12. A resonant screen device of the character described in claim 11, wherein said connection between said one of said resilient members and its supported deck connects the latter resiilent member in load supporting relationship to said battery bracket member.

13. A resonant screen device of the character described in claim 10, wherein at least one of said butter elements is connected to said bracket and at least one of said buffer elements is connected to said rod, with said rod extending through said bracket member; said bracket member and 25 the buffer elements respectively connected to said bracket member and said rod having central openings surrounding said rod, said openings being of a size relative to said rod sufiicient to permit rapid transfer of air under pressure along said rod within said bracket and said elements, the latter butter elements and the bracket and rod being associated such that there is a passage for air in communication with said openings along said rod extending outwardly of said buffer elements to the atmosphere at all times during the operation of said screening device.

References Cited by the Examiner UNITED STATES PATENTS 1,997,499 4/1935 Schieferstein 209315 X 2,183,660 12/1939 Symons 209-415 2,208,596 7/1940 Parks 209- 365 2,299,661 10/1942 Symons 209415 2,839,193 1/1958 Bruderlein 209-365 2,893,559 7/1959 Teuteberg 209-365 FOREIGN PATENTS 548,406 8/1954 Canada. 1,078,364 3/1960 Germany.

413,689 7/1934 Great Britain.

510,532 8/1939 Great Britain.

698,223 10/1953 Great Britain.

806,441 12/1958 Great Britain.

HARRY B. THORNTON, Primary Examiner.

FRANK W. LUTTER, Examiner.

R. HALPER, Assistant Examiner. 

7. A RESONANT SCREEN DEVICE, COMPRISING, IN COMBINATION: A PAIR OF VERTICALLY SPACED SCREEN DECKS MOVABLE RELATIVE TO EACH OTHER, EACH OF SAID DECKS HAVING SIDE PLATES AND CROSS BEAM MEMBERS AND SCREENS SUPPORTED BY SAID CROSS BEAM MEMBERS, THE CROSS BEAM MEMBERS OF EACH DECK BEING CONNECTED TO THE SIDE PLATES OF ITS ASSOCIATED DECK; AN INTERDECK BATTERY SYSTEM COMPRISING BUFFER MEMBERS INCLUDING RESILIENT ELEMENTS; MEANS CONNECTING SAID RESILIENT BUFFER ELEMENTS TO SAID DECKS FOR REACTION BETWEEN SAID BUFFER ELEMENTS WITHIN THE RESONANT RANGE OF OPERATION OF SAID DECKS; SAID CONNECTING MEANS INCLUDING ONE OF SAID CROSS BEAM MEMBERS OF ONE OF SAID DECKS AND AN OPERATING ROD CONNECTED TO THE LATTER CROSS BEAM MEMBER, SAID ROD EXTENDING ALONGSIDE OF SAID SCREEN DECKS; AT LEAST ONE OF SAID BUFFER ELEMENTS BEING CONNECTED TO SAID ROD AND LEAST ONE OF SAID BUFFER ELEMENTS BEING CONNECTED TO THE OTHER OF SAID DECKS, THE LATTER OF SAID ELEMENTS BEING REACTABLE WITH SAID ONE OF SAID BUFFER ELEMENTS TO CAUSE INTERDECK ACTION WHEN SAID SCREEN IS OSCILLATED IN THE RESONANT RANGE. 